Figure 8

Center-channel potential (solid line) and energy level spacing (dashed lines) over the course of the pumping cycle at a fixed exit gate voltage. The energy level spacing increases from capture as the curvature of the quantum dot increases. (i) The high exit barrier in the CPR suppresses pumping. (ii) The exit barrier in the LPR with zero bias voltage is low enough to allow a single electron to be pumped. (iii) Applying a forward bias of 100 mV in the LPR lowers the exit barrier allowing multiple electrons to be pumped